Molecular insights into leaf-wide senescence-like responses induced by a phloem-limited virus in melon

Cucurbit aphid-borne yellows virus (CABYV), a phloem-limited polerovirus, has become an increasingly significant constraint on cucurbit production worldwide. However, efforts to elucidate its molecular biology and pathogenic mechanisms have been hindered by the lack of reliable molecular tools. In this study, we generated a biologically active infectious cDNA clone of CABYV by precisely engineering the CaMV 35S promoter–viral genome junction; notably, the addition of two guanine residues immediately downstream of the promoter was essential for producing fully infectious viral transcripts. Using this optimized infectious clone, we established a highly reproducible Agrobacterium -mediated inoculation system for Cucumis melo , enabling uniform and synchronous CABYV infections suitable for high-resolution transcriptomic analysis. Using this controlled infection system, we performed RNA-seq analysis on CABYV-infected leaves exhibiting characteristic yellowing symptoms and found that CABYV infection triggers extensive, leaf-wide transcriptomic reprogramming, leading to physiological changes strikingly reminiscent of leaf senescence. Furthermore, exogenous cytokinin application effectively alleviated yellowing symptoms and restored chlorophyll content in CABYV-infected plants to levels comparable to those of healthy plants, despite having no significant effect on viral accumulation. Collectively, this study provides a robust experimental platform for investigating CABYV–host interactions and offers a comprehensive molecular and physiological framework for under the senescence-like yellowing symptoms characteristic of CABYV-infected C. melo .